The present invention relates to a system for cooling a high power or takeoff fuel injector portion of a dual fuel injector used in a dual head combustion chamber of a gas turbine engine.
In modern jet powered aircraft, a dual head combustion chamber is used in the turbojet engine to achieve the required pollution control levels, while at the same time obtaining optimal performance of the engine. The dual head combustion chambers are fed with fuel by way of a dual injector comprising a first or low power fuel injector for injecting fuel into the low power portion of the dual head combustion chamber and a second, high power, or takeoff, fuel injector for injecting fuel into the enhanced performance portion of the dual head and combustion chamber.
In such dual head combustion chambers, the low power fuel injector is permanently supplied with fuel regardless of the operating mode of the gas turbine engine. However, the high power or takeoff fuel injector is supplied with fuel only when the engine is operated beyond a specific minimum operating mode, generally corresponding to approximately 20% of the nominal operating mode. Accordingly, during operation in the low power mode, the high power fuel injector must be suitably cooled, particularly in the nozzle portion containing the fuel injector orifices in order to avoid encoking of the fuel and to preclude fuel vapor locks.
It is known to provide a cooling system for the high power fuel injector by circulating fuel feeding the low power injector inside the high power fuel injector, thereby cooling the high power injector. However, in the known applications, it is only the fuel in the primary circuit of the low power fuel injector which circulates through the high power fuel injector. The known fuel injectors are double flow for each module aeromechanical injectors. The fuel supply circuit in the low power fuel injectors comprises two coaxial tubes and the high power injector is supplied by a third tube at the center of the first two coaxial tubes and which communicates with the combustion chamber through fuel injection orifices in the nozzle terminal. The location of these orifices is far from the passage between the ends of the first two tubes and the cooling of this area is not entirely satisfactory.